Amazon doesn't need to pay leases or mortgages; they don't have a small army of sales clerks; they don't have to pay liability or fire or flood insurance on 650 stores; they only have to stock a handful of warehouses, rather than warehouses and 650 stores.

They also don't have to worry about digital cannibalizing their existing sales infrastructure.

And of course, indie stores don't have all the advantages of B&N or Amazon.